高能量密度锂离子电池结构工程化技术探讨

The structural engineering for achieving high energy density Li-ion batteries

基于商业化应用的锂离子电池材料体系,对电池结构进行工程化设计优化,是目前提升锂离子电池能量密度的重要研究方向。本文对比了电池尺寸、集流体厚度、N/P比和电极厚度等工程化因素在提升电池能量密度方面的潜力及风险,表明增加电极厚度是提高电池能量密度的主要工程化技术途径,但随之会带来电池倍率和寿命等性能下降的问题;基于此,从多孔电极理论出发,重点分析了影响厚电极电池性能的电极结构因素,综述了实用化厚电极的可能实现途径。综合分析表明,通过激光刻蚀、多层涂布等工程化技术,构建具有低曲折度、梯度孔隙率分布结构的实用化厚电极,有望实现厚电极在提高锂离子电池能量密度的同时兼顾电池倍率和寿命等性能。

Electric vehicle(EV)market has had an aggressive development in the last years,and Chinese market has more than 50%share of global capacity.However,there are still some important social barriers that must be overcome to get the expected BEV market penetration,mostly related to the cost,distance range capacity,charging time and infrastructure.Range anxiety is a key reason that consumers are reluctant to embrace EVs.To be truly competitive with gasoline vehicles,EVs should allow drivers to recharge quickly anywhere in any weather,like refueling gasoline cars,or carry more useful energies with high energy density lithium-ion batteries(LIBs).The need to improve performances and reduce costs of LIBs encourages different research strategies.In general,the methods toward achieving higher energy density LIBs can be summarized in two ways:①the development of novel battery chemistries with higher specific capacity and②the exploration of advanced battery configurations with increased electrochemical active material ratio via electrode architecture engineering.However,the novel battery chemistries have a long journey to be used industrially,structural engineering provides a feasible and universal way to further improve the energy density of LIBs without changing the fundamental battery chemistries.Recently the attention is focusing on increasing the electrodes areal capacity to enable the substantial reduction of the current collectors,porous separator,and electrolyte resulting in large gravimetric and volumetric energy density improvements as well as cost savings.Moreover,increasing electrode thickness and density is a most effective approach to achieve high energy density of LIBs,but high tortuosity and low wettability in the electrodes deteriorate the LIB performance,such power density and cycling life.Herein,we introduce various methods to create low tortuosity nanostructures,such as templating and micro fabrications,and the structural designs by adopting laser-structured or multi-layer coating technologies to realize a low tortuosity electrode in the commercialized LIBs are highlighted.